Require mbstring

Author: oleibman

.github/workflows/php.yml

@@ -75,7 +75,7 @@ jobs:
           uses: shivammathur/setup-php@v2
           with:
               php-version: ${{ matrix.php }}
-              extensions: gd, xml, zip
+              extensions: dom, gd, mbstring, xml, zip
               coverage: ${{ (matrix.php == '7.3') && 'xdebug' || 'none' }}
 
       -   uses: actions/checkout@v2

composer.json

@@ -109,8 +109,9 @@
         "php": "^7.1|^8.0",
         "ext-dom": "*",
         "ext-gd": "*",
-        "ext-zip": "*",
+        "ext-mbstring": "*",
         "ext-xml": "*",
+        "ext-zip": "*",
         "phpoffice/math": "^0.3"
     },
     "require-dev": {